In a typical internal combustion engine, a number of valves are mounted in valve openings in a cylinder head, with the valves being biased to a closed position by means of a compression spring that is retained in place by a spring retainer on the tip or outer end of the valve stem. The spring retainer has a tapered opening and is retained on the valve tip by a device called a keeper or valve lock. A valve lock is a sleeve formed into two sections that has one or more ridges on an internal surface that fit in corresponding grooves in the tip of the valve. A valve lock has a tapered exterior surface that mates with the tapered opening in the spring retainer, such that when the spring retainer is urged outwardly by the spring, the tapered opening in the spring retainer clamps against the valve lock and is retained in place.
The spring characteristics of the valve spring are important to the operation of a valve. When a spring becomes old and weak, it loses compression strength and the characteristics of the valve operation deteriorate.
A similar problem arises when an engine is rebuilt. During the cylinder head rebuilding process, both the valve face and valve seat are resurfaced to insure a good seal. This process is sometimes referred to as a "valve job". The operation is always part of the cylinder head remanufacturing process. Because of the grinding process, the valve "sinks" further into the cylinder head. This means that the valve tip protrudes further on the opposite side of the cylinder head. Because the valve tip protrudes further than originally engineered, the valve spring will not be as compressed. To compensate for this, cylinder head rebuilders shim the underside of the valve spring with a shim shaped like a washer in order to reduce the distance from the head to the tip of the valve stem. This is a standard practice throughout the industry. Generally, rebuilders will use a thirty thousandths (0.030) inch shim when new valve springs are being installed and a sixty thousandths (0.060) inch shim when the old springs are used. Since used springs relax slightly over time, a larger shim is necessary in order to compensate both for the grinding of the valves and the lower compression strength of the used spring. The use of shims is an added component and an added expense in the rebuilding process and introduces some heat dissipation considerations by the introduction of a dissimilar metal between the spring and the cylinder head.
An object of the present invention is to eliminate the use of shims in the valve grinding and engine remanufacturing processes.